1. Field of the Invention
This invention relates to systems for locating, identifying and tracking objects. More particularly, it related to aircraft location, identification and docking guidance systems and to ground traffic control methods for locating and identifying objects on an airfield and for safely and efficiently docking aircraft at such airport.
2. Description of Related Art
In recent years there has been a significantly increased amount of passenger, cargo and other aircraft traffic including take offs, landings and other aircraft ground traffic. Also, there has been a marked increase in the number of ground support vehicles which are required to off load cargo, provide catering services and on going maintenance and support of all aircraft. With this substantial increase in ground traffic has come a need for greater control and safety in the docking and identification of aircraft on an airfield.
Exemplary of prior art systems which have been proposed for detecting the presence of aircraft and other traffic on an airfield are those systems disclosed in U.S. Pat. No. 4,995,102; European Patent No. 188 757; and PCT Published Applications WO 93/13104 and WO 93/15416.
However, none of those systems have been found to be satisfactory for detection of the presence of aircraft on an airfield, particularly, under adverse climatic conditions causing diminished visibility such as encountered under fog, snow or sleet conditions. Furthermore, none of the systems disclosed in the prior references are capable of identifying and verifying the specific configuration of an approaching aircraft. Still further, none of the prior systems provide adequate techniques for tracking and docking an aircraft at a designated stopping point such as an airport loading gate. Also, none of the prior systems have provided techniques which enable adequate calibration of the instrument therein.
The system disclosed in the above-cited parent application seeks to overcome the above-noted problems though profile matching. Light pulses from a laser range finder (LRF) are projected in angular coordinates onto the airplane. The light pulses are reflected off the airplane to detect a shape of the airplane or of a portion of the airplane, e.g., the nose. The detected shape is compared with a profile corresponding to the shape of a known model of airplane to determine whether the detected shape corresponds to the shape of the known model.
However, that system has a drawback. Often, two or more models of airplanes have profiles so similar that one model is often misidentified as another. In particular, in adverse weather, many echoes are lost, so that profile discrimination becomes decreasingly reliable. Since the models are similar but not identical in body configuration, a correct docking position for one can cause an engine on another to crash into a physical obstacle.
Thus, it has been a continuing problem to provide systems which are sufficiently safe and reliable over a wide range of atmospheric conditions to enable detection of objects such as aircraft and other ground traffic on an airfield.
In addition, there has been a long standing need for systems which are not only capable of detecting objects such as aircraft, but which also provide for the effective identification of the detected object and verification of the identity of such object, for example, a detected aircraft with the necessary degree of certainty regardless of prevailing weather conditions and magnitude of ground traffic.
There has also been a long standing, unfulfilled need for systems which are capable of accurately and efficiently tracking and guiding objects such as incoming aircraft to a suitable stopping point such as an airport loading gate. In addition, the provision of accurate and effective calibration techniques for such systems has been a continuing problem requiring resolution.